Tropical Storm JOSEPHINE

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TROPICAL STORM JOSEPHINE DISCUSSION NUMBER 9
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL102008
500 AM EDT THU SEP 04 2008
CONVENTIONAL AND MICROWAVE SATELLITE IMAGERY INDICATE THAT DEEP
CONVECTION HAS REDEVELOPED IN THE NORTHERN SEMICIRCLE AND THAT THE
LOW-LEVEL CENTER HAS MOVED FURTHER INTO THE SOUTHERN PORTION OF THE
CONVECTIVE CLOUD MASS. SATELLITE INTENSITY ESTIMATES ARE T3.5/55 KT
AND T3.0/45 KT FROM TAFB AND SAB...RESPECTIVELY...SO THE INITIAL
INTENSITY HAS BEEN INCREASED TO 50 KT. HOWEVER...IF THE LOW-LEVEL
CENTER IS FARTHER NORTH INTO THE CONVECTION...THEN JOSEPHINE WILL
BE STRONGER THAN INDICATED IN THIS ADVISORY.
THE INITIAL MOTION ESTIMATE IS 285/9...BASED MAINLY ON MICROWAVE
SATELLITE POSITION ESTIMATES OVER THE PAST 9 HOURS. JOSEPHINE IS
FORECAST TO MOVE IN A GENERAL WEST-NORTHWESTWARD MOTION ALONG THE
SOUTHERN PERIPHERY OF LARGE SUBTROPICAL RIDGE FOR THE NEXT 48-72
HOURS. AFTER THAT...A WEAKNESS IS FORECAST TO DEVELOP IN THE RIDGE
...WHICH SHOULD ALLOW JOSEPHINE TO MAKE A POLEWARD JOG AT DAYS 3 AND
4...BEFORE THE RIDGE FILLS BACK IN FORCING THE CYCLONE ON A LITTLE
MORE WESTWARD BY 120 HOURS. THE OFFICIAL FORECAST TRACK IS TO THE
RIGHT OF THE PREVIOUS TRACK...BUT REMAINS TO THE LEFT OF THE MODEL
CONSENSUS AND CONTINUES ALONG THE SOUTHERN EDGE OF THE NHC MODEL
GUIDANCE ENVELOPE.
ALTHOUGH JOSEPHINE IS EXPERIENCING SOUTH-SOUTHWESTERLY VERTICAL WIND
SHEAR OF 20 TO 25 KT...THE CYCLONE IS LOCATED IN A REGION OF
MODERATE DIFLUENCE IN SOUTHEASTERN QUADRANT OF A LARGE UPPER-LEVEL
LOW THAT IS SITUATED ABOUT MIDWAY BETWEEN JOSEPHINE AND MAJOR
HURRICANE IKE. THIS UPPER-AIR PATTERN IS FORECAST TO PROPAGATE
WESTWARD IN TANDEM WITH JOSEPHINE AND IKE FOR THE NEXT 48 HOURS...
AFTER WHICH THE UPPER-LEVEL LOW IS EXPECTED TO GRADUALLY FILL AND
LIFT OUT TO THE NORTH. THE SHIPS INTENSITY MODEL MAINTAINS
SOUTHERLY SHEAR OF ABOUT 20 KT THROUGH 72 HOURS...AND THEN
INDICATES THE VERTICAL SHEAR WILL DECREASE TO 10 TO 15 KT AFTER
THAT. THE OFFICIAL FORECAST FOLLOWS THE SHIPS MODEL BY HOLDING THE
INTENSITY STEADY THROUGHOUT THE FORECAST PERIOD. HOWEVER...IF
JOSEPHINE REMAINS NEAR OR SOUTH OF 20N LATITUDE BY DAYS 4 AND
5...THEN THE CYCLONE WILL BE BENEATH UPPER-LEVEL ANTICYCLONIC FLOW
AND WEAK SHEAR...WHICH WOULD ALLOW FOR STRENGTHENING TO OCCUR. THIS
SCENARIO WILL BE EVALUATED IN SUBSEQUENT FORECAST PACKAGES.
FORECAST POSITIONS AND MAX WINDS
INITIAL 04/0900Z 14.2N 31.3W 50 KT
12HR VT 04/1800Z 14.5N 32.9W 50 KT
24HR VT 05/0600Z 15.0N 35.0W 50 KT
36HR VT 05/1800Z 15.7N 37.1W 50 KT
48HR VT 06/0600Z 16.4N 39.1W 50 KT
72HR VT 07/0600Z 17.9N 42.8W 50 KT
96HR VT 08/0600Z 19.5N 47.0W 50 KT
120HR VT 09/0600Z 21.0N 51.5W 50 KT
$$
FORECASTER STEWART
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